A charge coupled device is a semiconductor apparatus used for storing and sequentially transferring charges, representing information, between potential wells created adjacent the surface of the semiconductor body under a dielectric layer. These potential wells are induced by the sequential application of voltages to an array of conducting electrodes located on top of the dielectric layer adjacent the semiconductor body, and interconnected to establish a two-phase, three-phase or four-phase operation.
Two-phase CCD structures employing differential gate insulator thicknesses to produce a different interface potential for a given gate voltage are generally well known. These structures usually have overlapping electrodes isolated from each other by a dielectric material and are connected in pairs. Sometimes they also have ion implanted regions in the substrate which are self aligned with a first set of electrodes. The two sets of electrodes either partially overlap each other or have small interelectrode gaps. When they overlap, they produce a coupling capacitance, which permits the feedthrough of clock voltages and degrades the performance of the device, especially at high frequencies. When interelectrode gaps exist, the charge transfer efficiency of the device is degraded.
In addition, very often the frequency response of a CCD structure is limited by the response of its output MOS transistors.